Low-Frequency 3D Wave Propagation Modeling of the 12 May 2008 Mw 7.9 Wenchuan Earthquake

Abstract

The seismic potential of southern China is associated with the collision between the Indian and the Eurasian plates. This is manifested in the western Sichuan Plateau by several seismically active systems of faults, such as the Longmen Shan. The seismicity observed on the Longmen Shan fault includes recent events with magnitudes of up to 6.5, and the one of 12 May 2008 Mw 7.9 Wenchuan earth- quake. Herewith, as part of an ongoing research program, a recently optimized three- dimensional (3D) seismic wave propagation parallel finite-difference code was used to obtain low-frequency (≤ 0:3 Hz) 3D synthetic seismograms for the Wenchuan earthquake. The code was run on KanBalam (Universidad Nacional Autonoma de Mexico, Mexico) and HECToR (UK National Supercomputing Service) supercompu- ters. The modeling included the U.S. Geological Survey 40 × 315 km 2 kinematic description of the earthquake's rupture, embedded in a 2400 × 1600 × 300 km 3 phys- ical domain, spatially discretized at 1 km in the three directions and a temporal dis- cretization of 0.03 s. The compression and shear wave velocities and densities of the geologic structure used were obtained from recently published geophysical studies performed in the Sichuan region. The synthetic seismograms favorably compare with the observed ones for several station sites of the Seismological and Accelerographic Networks of China, such as MZQ, GYA, and TIY, located at about 90, 500, and 1200 km, respectively, from the epicenter of the Wenchuan event. Moreover, the com- parisons of synthetic displacements with differential radar interferometry (DinSAR) ground deformation imagery, as well as of maximum velocity synthetic patterns with Mercalli modified intensity isoseist of the 2008 Wenchuan earthquake, are acceptable. 3D visualizations of the propagation of the event were also obtained; they show the source rupture directivity effects of the Mw 7.9 Wenchuan event. Our results partially explain the extensive damage observed on the infrastructure and towns located in the neighborhood of the Wenchuan earthquake rupture zone.